The present invention relates to a three-dimensional observation apparatus and a three-dimensional observation system of the type that enables an individual to make three-dimensional (hereinafter 3-D) observations without using glasses. Previously, an observation apparatus as disclosed in Japanese Laid-Open Patent Publication S51-24116 has been proposed for such a 3-D observation apparatus. As shown in FIG. 32, this observation apparatus comprises two display apparatuses 51R and 51L, two concave mirrors 52R and 52L, and a single concave mirror 53 that faces the concave mirrors 52R and 52L. The concave mirrors 52R and 52L are designed and positioned so that the radii of curvature and the centers of curvature thereof match. In FIG. 32, reference numbers 54R and 54L designate the right and left pupils, respectively, of an observer.
FIG. 33 is a side view of the observation apparatus illustrated in FIG. 32. In FIG. 33, the top and bottom have been reversed in order to simplify understanding its operation and, in addition, the display apparatus has been omitted from the drawing. Furthermore, in FIG. 33 reference numbers 54R′ (54L′) and 54R″ (54L″) indicate conjugate positions of the observer's pupils. Each of the display apparatuses 51R (51L) shown in FIG. 32 is positioned in the range from the position PR(∞) (PL(∞)) (i.e., at infinity) to the focal point PR(f) (PL(f)) shown in FIG. 33. When the display apparatuses 51R (51L) are placed at the position PR(∞) (PL(∞)), light emitted from the display apparatuses 51R (51L) is reflected by the concave mirrors 52R (52L) and then forms an image at the front-side focal position A of the concave mirror 53. Furthermore, the light is then reflected by the concave mirror 53 and is guided to the observer's pupils 54R (54L) as substantially collimated light rays. When the display apparatuses 51R (51L) are placed at the front-side focal position PR(f) (PL(f)) of the concave mirrors 52R (52L), light emitted from the display apparatuses 51R (51L) is reflected by the concave mirrors 52R (52L) and becomes substantially collimated. Furthermore, after being reflected by the concave mirror 53, the light forms an image at the back-side focal point B of the concave mirror 53. Following this, the image spreads and is guided to the observer's pupils 54R (54L).
Furthermore, as this kind of conventional observation apparatus does not use a half-mirror, bright 3-D images may be obtained. However, with such a conventional 3-D observation apparatus, it is impossible to observe at one position while substantially in the same posture, the observation images from different display apparatuses. In addition, it is impossible to make multi-surface observations such as observations that allow 2-D images and 3-D images to be observed while substantially in the same posture.
Moreover, with the above-described 3-D observation apparatus, there are two concave mirrors that create distortions in the image, and consequently the positioning of the two concave mirrors which face each other is limited to positions that mutually compensate for this distortion. With this type of arrangement, distortion of the image and size of fluctuations in the focal point are determined in response to errors in installing the concave mirrors. In order to mitigate such problems, the surface precision of the concave mirrors must be kept high, while errors in installing the two concave mirrors must be kept extremely small. However, this results in high manufacturing and installation costs for the mirrors.
In addition, because the surface that the observer faces is that of a concave mirror, image distortion is large with respect to differences in observation position. Consequently, there is no freedom in observation position. This results in the observer's posture also being restricted, and results in observations being somewhat inconvenient.
Furthermore, in order to increase freedom in observation, it is necessary to enlarge the exit pupils. However, in an observation apparatus having the above-described design, enlarging the exit pupils requires that the concave mirrors be enlarged. Consequently, this results in the display apparatus as a whole becoming larger.